The long-term objectives of the proposed research program are: (1) a classification of developmental disease of the nervous system based upon pathologic processes at the cellular level and (2) a definition of abnormality in pathologic specimens in terms of cellular and subcellular structure. Work involves the analysis of cortical abnormalities in human specimens and in the mutant mouse. The immediate task has been extract from cellular structure in human specimens information about the time of action of pathologic processes and to identify the cellular and subcellular tissue elements affected by each process. Research in the reeler mutant mouse is concerned with the morphogenetic events through which relative cell position is achieved in cortical structures, as well as the morphologic consequences of cell malposition. An organizing theme will be interactions of the individual neuron with other cellular elements under normal and pathologic circumstances. BIBLIOGRAPHIC REFERENCES: Caviness, V.S., Jr., Korde, M.G., Williams, R.S., 1977, Cellular events induced by ablation of the olfactory bulb in the molecular layer of the piriform cortex of the mouse. Brain Res., in press. Williams, R.S., Ferrante, R. J., Caviness, V.S., Jr., 1977, Cellular pathology of late infantile neuron ceroid-lipofuscinosis: a Golgi and electron microscopic study. Arch. Neurol., in press.